Percussion power press

ABSTRACT

A percussion power press wherein the base guides two vertically reciprocable columns of a frame whose upper crosshead carries the punch and whose lower crosshead is coupled to and movable relative to the base by several hydraulic cylinders. The columns, which cannot rotate about their axes, are provided with external threads mating with internal threads of flywheels which rotate in response to movement of the frame. The flywheels rotate on thrust bearings which are installed in recesses provided therefor in the base, and they displace plungers in stationary gas-filled cylinders when the downward movement of the frame is terminated or slowed down while the flywheels continue to rotate.

United States Patent [72] Inventors Appl. No. Filed Patented Assignee Priority PERCUSSION POWER PRESS 10 Claims, 5 Drawing Figs.

Int. Cl. B301) l/34, 1330b 15/16 Field of Search 100/270, 27l;83/701,615;72/453,454

Primary Examiner-William 1. Price Attorney-Michael S. Striker ABSTRACT: A percussion power press wherein the base guides two vertically reciprocable columns of a frame whose upper crosshead carries the punch and whose lower crosshead is coupled to and movable relative to the base by-several hydraulic cylinders. The columns, which cannot rotate about their axes, are provided with external threads mating with internal threads of flywheels which rotate in response to movement of the frame. The flywheels rotate on thrust bearings which are installed in recesses provided therefor in the base, and they displace plungers in stationary gas-filled c/linders when the downward movement of the frame is termiriated or slowed down while the flywheels continue to rotate.

PATENTED JUH29 Ian 589278 SHEET 3 BF 4 FIG. 3

18c 18b 3b Ham B I!!! mere/z HA-Lb M13 11 PERCUSSION POWER PRESS BACKGROUND OF THE INVENTION The present invention relates to percussion power presses in general, and more particularly to improvements in so-called dieing machines wherein the movable die or punch is pulled, rather than pushed, toward the stationary die.

The efficiency of many presently known percussion power presses is rather low, mainly owing to friction and the resulting generation of heat during acceleration and deceleration of the flywheel. Attempts to improve the efficiency of such presses include the provision of an electric motor which is directly coupled to the spindle for the flywheel so that the flywheel need not be rotated by friction discs or the like. It is also known to provide a percussion power press of the type wherein the punch receives motion from one or more hydraulic cylinders with a flywheel which is effective only while the punch performs a working stroke but is disengaged from the spindle when the punch moves away from the stationary die. REference may be had to German Pat. No. 729,451.-

It is further known to mount the spindle and the flywheel of a percussion power press below the stationary die. An advantage of such construction is that the torque which the frame for the punch transmits to the stationary part of the machine is communicated to the foundation along a relatively short path. This renders it possible to employ a lighter stationary part. Moreover, such mounting of the spindle and flywheel lowers the center of gravity. The upper crosshead of the frame carries the punch and the stationary part of the press constitutes a base for the stationary die. The base is pro vided with guide means for the frame and the spindle is rotatably mounted in and extends downwardly from the base and is rigid with the flywheel. A hydraulic cylinder is used to pull the punch to ward the stationary die to thereby set the spindle and the flywheel in rotary motion. Torque which is transmitted to the frame on rotation of the spindle and flywheel is taken up by the base which must be provided with long guides for the frame and must practically surround the entire frame. This contributes to the bulk, weight and cost of the base. Reference may be had to German printed publication No. 1,277,672.

SUMMARY OF THE INVENTION An object of the invention is to provide a percussion power press of the type wherein the punch is pulled toward the stationary die and to construct and assemble the press in such a way that it can utilize a lighter base and shorter guide means for the movable frame than heretofore known presses of equal capacity.

Another object of the invention is to provide a percussion power press which can employ a single stationary die and a single punch or two more pairs of such parts and wherein the workpieces can be shaped properly regardless of whether or not they are placed onto the exact center of the base.

A further object of the invention is to provide a percussion power press with novel means for receiving torque which develops on rotation of the flywheel or flywheels.

An additional object of the invention is to provide a percussion power press whose overall height is substantially less than the height of presently known presses having the same capacity.

The invention is embodied in a percussion power press which comprises a fixed die-supporting base, a frame including a punch-supporting upper crosshead located above the base, a lower crosshead located below the base, and a plurality of preferably vertical columns reciprocably guided by the base and connecting the crossheads to each other, external threads provided on at least one of the columns, flywheel means ineluding an internally threaded flywheel meshing with the threads of the one column and arranged to rotate in response to lengthwise movement of the columns with reference to the base, drive means arranged to move the frame up and down with reference to the base and preferably including one or more hydraulic cylinder assemblies coupling the base with the lower crosshead, and confining means provided on the base for limiting the extent of axial movement of the flywheel.

The confining means preferably comprises a thrust bearing interposed between the flywheel and the base and located below the flywheel, and a plunger located above and in the path of axial movement of the flywheel and extending into a gas-filled cylinder in the base to penetrate in to the cylinder and to further compress the gas therein when the downward movement of the frame is terminated. or slowed down to such an extent that the flywheel moves axially upwardly relative to the one column.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved percussion power press itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is a central longitudinal vertical sectional view of a percussion power press which embodies the invention;

FIG. 2 is a transverse vertical sectional view as seen in the direction of arrows from the line A-B of FIG. 1;

FIG. 3 is an end elevational view of the press as seen from the right-hand side of FIG. 1, with certain parts partially broken away;

FIG. 4 is an enlarged view ofa detail in FIG. 1; and

FIG. 5 illustrates the hydraulic circuit of the press.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 3, there is shown a percussion power press which comprises an upper crosshead 1 serving to support the upper die or punch (not shown), a base or bed 7 which supports the lower die (not shown), a pair of upright columns or tie rods 2, 3 which are rigid with the upper c osshead 1 and are slidably guided in the base 7, a lower crosshead or bridge 4 which extends between and connects the lower end portions of the columns 2, 3 to each other, and two internally threaded flywheels 2b, 3b which constitute spin dle nuts and respectively mesh with externally threaded median portions 2a, 3a of the columns 2, 3. Bearing sleeves 5, 5a and 6, 6a in the base 7 respectively serve to guide the columns 2, 3 for vertical movement with reference to the base whereby the crosshead I and the bridge 4 share such movements. Ringshaped springs 8, 9 are mounted in the crosshead l in a manner known per se to hold the columns 2, 3 against rotation about their axes. The lower ends of the column 2, 3 are externally threaded to take nuts 10, 11 which support the bridge 4 from below. The drive means for reciprocating the frame including the crosshead 1, bridge 4 and the columns 2, 3 comprises two double-acting hydraulic cylinders 12, 13 which are attached to and extend downwardly from the base 7, pistons 12a, 13a which are reciprocable in the cylinders 12, 13, and piston rods 12b, 13b which are attached to the bridge 4 in a manner shown in the lower part of FIG. 1. The means for admitting pressurized hydraulic fluid to and for evacuating fluid from the cylinders 12, 13 comprises pairs of conduits 14, 14a and 15, 15a best shown in FIG. 5.

The flywheels 2b, 3b respectively rest on the upper races of thrust bearings 16, which are mounted in recesses 7A, 78 provided in the base 7. During overloading of the press, the upper end faces of the flywheels 2b, 3b respectively engage and displace ring-shaped plungers 17, which extend into cylinders 18, 18a mounted in the base 7. The chambers of the cylinders 18, 18a are filled with a compressed inert gas, such as nitrogen. The pressure of gas in the cylinders 18, 18a is selected in such a way that it corresponds to the nominal or rated tonnage of the press. The plungers 17, 17a bear against retaining rings 18b (FIG. 4) which are secured to the base 7 by screws or bolts ll8c. In the event of an overload, the flywheels 2b, 3b can move upwardly by depressing the plungers I7, 17a into the respective cylinders 18, 18a together constitute a confining structure which limits axial movements of the flywheels 2b, 3b relative to the base 7. The numerals I9, 19a denote shock absorbing cushions or bumpers which are provided on the columns 2, 3 at a level above the bridge 4 and can engage ring-shaped stops b, 6b which constitute covers for the lower bearing sleeves 5b, 6b and become effective only when the controls of the press are defective so that the columns 2, 3 move upwardly and beyond their normal upper end positions shown in FIG. 1.

FIG. 5 illustrates the hydraulic circuit of the press. For the sake of clarity, the drive means including the cylinders ll2, I3 is shown twice, namely, once with the piston rods 12b, 13b retracted and once with the piston rods extended. The circuit includes a pump 20 which is driven by an electric motor 21, three pressure limiting valves 23, 25, 25a, two pressure relief valves 22, 24, four adjustable check valves 26, 27, 28, 29 two solenoid-operated distributor valves or spool valves 30, 31, two pressure tanks 32, 33, a simple check valve 34, a flow restrictor 35, and several conduits including the aforementioned conduits 14, 14a, and 15a.

The operation:

In order to effect movement of the frame ll4 from the normal upper end position shown in FIG. 2, the operator adjusts the distributor valve 30 in such a way that the conduit 36 is connected with the conduits 37 and 37a. The pressurized fluid (e.g., oil) which is delivered by the pump is then free to flow through the check valve 34, conduit 38, adjustable check valve 29 (which is then open) and into the conduits I4, 15 to cause a downward movement of the pistons 12a, 13a and piston rods 12b, 13b whereby the bridge 4 moves downwardly and entrains the columns 2, 3 as well as the upper crosshead I. The fluid also flows through the pressure reducing valve 24 and conduit 46 into the tank 32. The valve 24 is adjusted in such a way that the fluid pressure in the tank 32 cannot reach the normal working pressure.

The fluid which is expelled from the cylinders 12, 13 into the conduits 14a, 15a flows through the adjustable check valve 26 (which is then open) into the conduit 39 and thence into the tank 32. When the pressure in the tank rises to a value which is determined by appropriate setting of the valve 23, the valve 23 opens and admits the remaining outflowing fluid into the reservoir R. The pressure which is selected by the valve 23 is well below the actual working pressure so that no fluid can flow from the conduit 39 into conduit 45, through the adjustable check valve 28 and into the conduits l4, 15.

The descending frame I-4 is provided with or transmits motion to an actuating member 40 which constitutes a trip and can actuate a series of limit switches 41a, 41b, 41c, 41d, 4Ie, 41f. These limit switches are connected with a selector 42 serving as a means for selecting that limit switch which causes a change in the direction of fluid flow into and from the cylinders 12, 13. Thus, the selected limit switch determines the exact moment when the frame l-4 begins to move upwardly toward the position shown in FIG. 1. Otherwise stated, the selector 42 enables the operator to determine the magnitude of the impact of the punch on the workpiece or workpieces on the base 7. For example, if the operator wishes the frame l-4 to perform a relatively long working stroke and to reverse the direction of its movement shortly before it reaches the lowermost end of its stroke, the selector 42 is set to select the limit switch 41a. This limit switch then changes the condition of the distributor valve 30 as soon as it is actuated by the trip 40 whe eby the valve 30 connects the conduit 36 with a conduit 43. This causes the adjustable check valves 27, 23 to assume their open position and the valves 26, 29 to reassume their closed or blocking positions. The fluid which is delivered by the pump 20 then flows through the conduits 38 and 44, valve 27 and conduits 14a, 15a to cause upward movement of the pistons 12a, 13a and piston rods 12b, 13b. Since the valve 28 is open, the fluid which flows from the cylinders 12, 13 into the conduits 14, 25 can flow into the conduits 45, 46 and the tank 32.

During the resulting upward movement of the frame 1-4, a second actuating member or trip 40a engages a limit switch 41 which causes the valve 30 to assume the neutral position shown in FIG. 5. This causes a drop of fluid pressure in the conduit 43 and results in closing or blocking of the check valves 27, 28. The fluid which is discharged from the cylinders 12, 13 by way of the conduits Z4, 15 must flow through the adjustable check valve 29 and enters the tank 33 by overcoming the pressure which is selected by the valve 25. The resistance which the out flowing fluid encounters during flow into the tank 33 results in a braking action which slows down the frame I-4 and the pistons 12a, 13a. This breaking action is valuable because the energy of rotating flywheels 2b, 3b is utilized to fill the tank 33 with pressurized fluid.

As the pistons 12a, 13a continue to move upwardly, the trip 40a on the frame I-4 actuates a further limit switch 41h which adjusts the distributor valve 31 in such a way that a conduit 47 communicates with a conduit 48. This permits the flow of a small quantity of fluid at low pressure into the conduits 14a, ISato effect movement of the pistons 12a, 13a to their upper end positions. The amount of fluid is determined by the flow restrictor 35 and its pressure by the valve 22. When the frame l-4 reaches its upper end position, the trip 40a actuates a further limit switch 4Ii which returns the valve 31 to the illustrated neutral position whereby the conduit 48 is sealed from the conduit 47 and the frame l-4 comes to a standstill to complete a working cycle.

As shown in FIG. I, the threads on one of the portions 2a, 3a are right-hand threads and the threads on the other of these portions are left-hand threads. Therefore, the flywheels 2b, 3b rotate in opposite directions regardless of whether the columns 2, 3 move up or down. The mounting of flywheels 2b, 3b in the recesses 7A, 7B of the base 7 renders it possible to reduce the overall height of the frame I4, and of the base.

Moreover, the base 7 need not completely surround the frame and it may be rather small because the flywheels rotate in opposite directions so that the stresses transmitted to the frame and base in response to rotation of one flywheel are balanced by stresses which develop on rotation of the other flywheel.

An advantage of the plungers I7, 117a and cylinders 18, 18a is that they require minimal maintenance and are always ready to take up and absorb stresses which develop in the event of an overload.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What we claim as new and desire to be protected by Letters Patent is set forth in the appended claims:

1. In a press, a combination comprising a die-supporting base; a frame including a punch-supporting upper crosshead located above said base, a lower crosshead located below said base, and a plurality of columns reciprocably guided in said base and connecting said crossheads to each other, at least one of said columns having an externally threaded median portion; flywheel means including an internally threaded flywheel meshing with said median portion and arranged to rotate in response to lengthwise movement of said columns; drive means for moving said frame up and down with reference to said base; and confining means provided on said base to limit the extent of axial movement of said flywheel.

2. A combination as defined in claim ll, wherein said columns are at least substantially vertical and are nonrotatably secured to said crossheads.

compressed gas and said yieldable member is a plunger extending into said cylinder and located in the path of axial movement of said flywheel.

7. A combination as defined in claim 1, wherein said drive means comprises at least one double-acting fluid-operated cylinder assembly connected between said base and said lower crosshead.

8. A combination as defined in claim 1, wherein said columns include a pair of columns each having an externally threaded median portion and wherein the threads of open of said pair of columns are right-hand threads and the threads of the other of said pair of columns are left-hand threads, said flywheel means comprising two flywheels each having internal threads mating with the external threads of one of said pair of columns so that said flywheels rotate in opposite directions in response to movement of said frame with reference to said base.

9. A combination as defined in claim 1, wherein said confining means are provided in a recess of said base.

10. A combination as defined in claim 1, further comprising shock absorber means interposed between said frame and said base to become effective when said frame moves up wardly beyond a predetermined normal upper end position. 

1. In a press, a combination comprising a die-supporting base; a frame including a punch-supporting upper crosshead located above said base, a lower crosshead located below said base, and a plurality of columns reciprocably guided in said base and connecting said crossheads to each other, at least one of said columns having an externally threaded median portion; flywheel means including an internally threaded flywheel meshing with said median portion and arranged to rotate in response to lengthwise movement of said columns; drive means for moving said frame up and down with reference to said base; and confining means provided on said base to limit the extent of axial movement of said flywheel.
 2. A combination as defined in claim 1, wherein said columns are at least substantially vertical and are nonrotatably secured to said crossheads.
 3. A combination as defined in claim 1, wherein said confining means comprises a thrust bearing interposed between said flywheel and said base.
 4. A combination as defined in claim 3, wherein said confining means further comprises a yieldable member interposed between said flywheel and said base opposite said bearing.
 5. A combination as defined in claim 4, wherein said bearing is disposed below and said yieldable member is disposed above said flywheel.
 6. A combination as defined in claim 5, wherein said confining means further comprises a cylinder containing a supply of compressed gas and said yieldable member is a plunger extending into said cylinder and located in the path of axial movement of said flywheel.
 7. A combination as defined in claim 1, wherein said drive means comprises at least one double-acting fluid-operated cylinder assembly connected between said base and said lower crosshead.
 8. A combination as defined in claim 1, wherein said columns include a pair of columns each having an externally threaded median portion and wherein the threads of open of said pair of columns are right-hand threads and the threads of the other of said pair of columns are left-hand threads, said flywheel means comprising two flywheels each having internal threads mating with the external threads of one of said pair of columns so that said flywheels rotate in opposite directions in response to movement of said frame with reference to said base.
 9. A combination as defined in claim 1, wherein said confining means are provided in a recess of said base.
 10. A combination as defined in claim 1, further comprising shock absorber means interposed between said Frame and said base to become effective when said frame moves upwardly beyond a predetermined normal upper end position. 